The aim of this paper is to present 24 almost forgotten handwritten manuscripts that were recently found in the library of the Mathematical Institute of the Serbian Academy of Sciences and Arts. These writings belong to the prominent professors of the Belgrade University who lectured pure and applied mathematics at the beginning of the previous century: Dimitrije Danić (1862-1932), two manuscripts on applied mathematics; Kosta Stojanović (1867-1921), two manuscripts on physics and geometry; Mihailo Petrović (1868-1943), 14 manuscripts on mathematics, mostly on differential calculus and algebra; Milutin Milanković (1879-1958), five writings on applied mathematics, physics, and theoretical mechanics and one manuscript by an unknown author. Digital copies of these writings are deposited in the Virtual Library of the Faculty of Mathematics of the University of Belgrade.